1. Field of the Invention
The invention relates to light responsive devices for developing an electrical output signal indicative of movement or vibration and, more particularly, but not by way of limitation, it relates to a motion sensing device that is responsive to either absorption or fluorescence of light radiation of predetermined wave lengths.
2. Description of the Prior Art
The prior art includes numerous types of motion sensing device which function in response to variation in light transmission. A relatively early form of seismic motion detector which was extremely sensitive to earth vibrations utilizes a laser light source for effecting light vibrations in response to extremely minimal vibrations as are detected and amplified for further processing. The U.S. Pat. No. 4,155,065 is considered to be of pertinence relative to the present invention as it is the closest related art known to Applicant albeit that it is not really anticipative of even the basic features of Applicant's invention. This patent teaches the use of a liquid having ceramic particles dispersed therein and utilizes the backscattering of laser energy to provide detector indication of acoustic signals. In this case, the suspended ceramic particles are oscillated by the impending acoustic waves at a particular frequency whereupon the backscattered light is detected and transformed into electrical signal output.